This proposal seeks to establish the relationship between specific neurochemical systems and central controls for feeding and body weight. Substantial evidence suggests that the catecholamines (norepinephrine and dopamine) are involved in the regulation of food intake and body weight. Lesions of catecholamine systems affect both variables. Recent work indicates that, with respect to lesion-produced increases in body weight, damage to noradrenergic neurons is not a sufficient condition to produce obesity, as originally suggested by some experiments. Apparently some accompanying damage to non-catecholamine neurons is necessary. Neither the neurochemical nor anatomical identity of these neurons is clear. The proposed plan of study is designed to determine the relationship between identified neurochemical systems and obesity. This will be accomplished by employing neurotoxins specific for particular systems to produce lesions of these systems. Neurochemical analyses of hypothalamus and telencephalon will be made to establish the neurochemical effects of the lesions in these brain regions. Possible relationships between the neurochemical, behavioral, and physiological variables will be explored. In addition studies employing various drugs used to control obesity will be conducted to determine their efficacy in altering weight levels in this particular obesity syndrome.